A focus on antisocial beliefs and attitudes has informed both the assessment and treatment literature, and practice, in youth justice service provision. This study attempts to broaden the construct of antisocial beliefs and attitudes and reports on the psychometric development of the Antisocial Beliefs and Attitudes Scale (ABAS). The ABAS is a new instrument for measuring antisocial thinking in older children and adolescents, which is developmentally-sensitive, broad-based, and assesses domains grounded in the empirical literature on childhood conduct problems and delinquency. Along with a self-reported measure of antisocial behavior, the ABAS was administered to 425 school children aged 10-18 (M = 14.18; SD = 2.31). A meaningful factor structure emerged from our instrument with two of the three factors, Rule Non-Compliance and Peer Conflict, predicting self-reported antisocial behavior while demonstrating sensitivity to age and gender. These findings are encouraging in our aim to "bridge" the measurement gap, by developing a reliable and valid measure of antisocial thinking applicable to older children and adolescents.